Electromagnetic hydraulic valve

Abstract

An electromagnetic hydraulic valve ( 1 ), in particular proportional valve, for controlling a device for the rotational angle adjustment of a camshaft relative to a crankshaft of an internal combustion engine, composed of an electromagnet ( 2 ) with a hollow-cylindrical magnet housing ( 4 ), at least one coil winding ( 5 ), an axially moveable magnet armature ( 6 ), a first and a second pole shoe ( 7, 8 ), a valve part ( 3 ) with a hollow-cylindrical valve housing ( 9 ) having a control piston ( 12 ) which can be moved axially by the magnet armature ( 6 ) of the electromagnet ( 2 ) via a plunger rod ( 11 ). The invention consists of a sleeve ( 17 ), composed of a base ( 18 ) and a hollow-cylindrical side wall ( 19 ), which is arranged on that end of the control piston ( 12 ) and situated in the direction of the plunger rod ( 11 ), where the sleeve ( 17 ) has a greater hardness than the control piston ( 12 ).

1. An electromagnetic hydraulic valve controlling a device for a rotational angle adjustment of a camshaft relative to a crankshaft of an internal combustion engine, comprising:
 an electromagnet having a hollow-cylindrical magnet housing, at least one coil winding, an axially moveable magnet armature, and a first and a second pole shoe; and 
 a valve part having a hollow-cylindrical valve housing in which is accommodated a control piston which can be moved axially by the magnet armature of the electromagnet via a plunger rod, with pressure medium connections being formed in the valve housing, which pressure medium connections can be connected to or separated from one another as a function of the position of the control piston, and with a return of the control piston being affected by a pressure spring which acts counter to a force of the magnet armature, 
 wherein a sleeve, which is composed of a base and a hollow-cylindrical side wall, is arranged on an end of the control piston which is situated in a direction of the plunger rod, and the sleeve has a greater hardness than the control piston, and 
 wherein the hollow-cylindrical side wall of the sleeve has, at an end remote from the base, a flanged edge which has a smaller wall thickness than the hollow-cylindrical side wall. 
 
     
     
       2. The electromagnetic hydraulic valve as claimed in  claim 1 , wherein the sleeve is produced from an iron material, is formed as a part which is produced in a non-cutting process, and undergoes a heat treatment in order to increase its hardness. 
     
     
       3. The electromagnetic hydraulic valve as claimed in  claim 1 , wherein a central elevation, which points in the direction of the plunger rod, is arranged in the base of the sleeve. 
     
     
       4. The electromagnetic hydraulic valve as claimed in  claim 1 , wherein the control piston is produced from a plastic or from a light metal. 
     
     
       5. The electromagnetic hydraulic valve as claimed in  claim 4 , wherein the control piston is connected to the sleeve by means of injection molding.